The present disclosure relates generally to a light fixture and associated LED (light emitting diode) board and monolithic optic useful for area lighting or street lighting, and particularly to an LED-based street light fixture capable of generating a Type-III emission pattern at the ground level.
Conventional street lights include acorn type light fixtures and cobra type light fixtures, with the acorn type fixtures typically casting light from a light source in a uniform distribution around a central vertical axis (the lamp post for example) toward the street, and the cobra type fixtures typically casting light in a uniform downward distribution toward the street from an overhanging light source. With light fixtures having unmodified light distribution, the light emission pattern on one side of the fixture is substantially identical to the light emission pattern on an opposite side of the fixture. For acorn type light fixtures, such a uniform light emission pattern at the ground level is an inefficient use of light and energy where more light on the street side of the lamppost and less light on the house side of the lamppost is desired. Also with respect to energy usage, streetlights that employ high-pressure sodium (HPS) technology can still require a substantial amount of energy that can be overly burdensome to the tax base of municipalities employing many street light fixtures.
In an effort to overcome each of the aforementioned drawbacks, an LED solution employing a Type-III emission pattern (more light directed toward the street side and less light directed toward the house side) has been sought after, with the energy efficiency of LED's serving to keep energy demands under control, and the use of a specific emission pattern also serving to keep energy demands under control by directing the light to where it is more useful and less objectionable. For street lighting, however, and in view of the limited lumen output of a single LED compared with the cost of many LED's, an efficient arrangement utilizing a plurality of LED's within a single light fixture, such as an acorn light fixture, along with directed light emission, is desirable for advancing the art of LED street lighting and overcoming the aforementioned drawbacks.